Re: How to get coefficient list from a Series Command

*To*: mathgroup at smc.vnet.net*Subject*: [mg114446] Re: How to get coefficient list from a Series Command*From*: Ray Koopman <koopman at sfu.ca>*Date*: Sat, 4 Dec 2010 06:16:23 -0500 (EST)*References*: <idakdb$m2u$1@smc.vnet.net>

On Dec 3, 3:30 am, Autt <kajornrungsil... at gmail.com> wrote: > Greeting, > I've a list issued from multivariate series like : K={a1+a2*x +a3*y > +a4*x^2*+a5*x*y +a6*y^2 } > I need to have {a1, a2 , a3 ,a4,a5,a6} > > How to do that please? > e.g. > n = 3 > u = Normal[Series[x^4 + y^4 + x^2, {x, 5, n}, {y, 5, n}]] > c[0] = {}; > d = {}; > q[0] = {}; > For[k = 1 , k <= n - 1, k++, > For[i = 0 , i <= k , i++, > p[i, k - i] = > SeriesCoefficient[u, {x, 5, i}, {y, 5, k - i}]; > q[k] = Union[{q[k - 1], {p[i, k - i]}}]; > d = Union[d, q[k]]; > > Print[d]; > > Best regard, c = CoefficientList[u,{x,y}] {{-1250,500,-150,20},{500,0,0,0},{-149,0,0,0},{20,0,0,0}} c[[i,j]] is the coefficient of x^(i-1)*y^(j-1). TableForm[c, TableHeadings->MapThread[#1^Range[0,#2-1]&, {{x,y},Dimensions@c}], TableAlignments->Right] 1 y y^2 y^3 1 -1250 500 -150 20 x 500 0 0 0 x^2 -149 0 0 0 x^3 20 0 0 0